H.E.S.S. Unidentified Gamma-ray Sources in a Pulsar Wind Nebula - PowerPoint PPT Presentation

H.E.S.S. Unidentified Gamma-ray Sources in a Pulsar Wind Nebula Scenario And HESS J1303-631 Matthew Dalton Humboldt University at Berlin For the H.E.S.S. Collaboration TeV Particle Astrophysics, Paris . July 2010

Overview The H.E.S.S. Telescopes The H.E.S.S. Telescopes Unidentified Gamma-ray sources as PWNe Unidentified Gamma-ray sources as PWNe HESS J1303-631 HESS J1303-631

H.E.S.S. High Energy Stereoscopic High Energy Stereoscopic System System Gamma-rays produce air Gamma-rays produce air showers which are imaged by showers which are imaged by Cherenkov telescopes Cherenkov telescopes Imaged showers are Imaged showers are reconstructed to produce sky reconstructed to produce sky maps and spectra of gamma- maps and spectra of gamma- ray sources ray sources

H.E.S.S. 4 Telescopes in Namibia 4 Telescopes in Namibia 13m diameter each 13m diameter each Gamma-rays from ~100 GeV to ~100 TeV Gamma-rays from ~100 GeV to ~100 TeV Angular Resolution: < 0.08 degrees per event Angular Resolution: < 0.08 degrees per event 5 degree field of view 5 degree field of view

Sources Detected with H.E.S.S. Most of the sources we see are: Most of the sources we see are: Supernova Remnants Supernova Remnants Active Galactic Nuclei Active Galactic Nuclei Pulsar Binary Systems Pulsar Binary Systems Pulsar Wind Nebulae Pulsar Wind Nebulae ... or unidentified ... or unidentified PWN: HESS J1825-137 PWN: HESS J1825-137 SNR RX J1713.7-3946 SNR RX J1713.7-3946

Unidentified Sources H.E.S.S. has also detected ~24 H.E.S.S. has also detected ~24 unidentified sources. unidentified sources. What could it be What could it be Unidentified Sources a PWN? a PWN? HESS J0632+057 HESS J1023-575 WR 20a; Westerlund 2; RCW 49 HESS J1303-631 HESS J1427-608 HESS J1614-518 HESS J1616-508 PSR J1617-5055 ? HESS J1626-490 HESS J1632-478 IGR J16320-4751 ? HESS J1634-472 IGR J16358-4726 ?; G337.2+0.1 ? HESS J1640-465 G338.3-0.0 ?; 3EG J1639-4702 ? HESS J1702-420 HESS J1708-410 HESS J1713-381 CTB 37B (G348.7+0.3) ? HESS J1714-385 CTB 37A HESS J1718-385 PSR J1718-3825 ? HESS J1745-290 Sgr A* / Chan PWN ? HESS J1745-303 3EG J1744-3011 ? HESS J1804-216 G8.7-0.1 / W30 ?; PSR J1803-2137 ? HESS J1809-193 PSR J1809-1917 ? HESS J1813-178 G12.8-0.02; AX J1813-178 HESS J1834-087 G23.3-0.3 / W41?

Unidentified Sources Type 1: Multiple and complex: Type 1: Multiple and complex: HESS J1745-303 appears to be numerous emission HESS J1745-303 appears to be numerous emission regions with several possible emission regions with several possible emission mechanisms. mechanisms. Possible Associations: Possible Associations: EGRET 3EG J1744-3022 EGRET 3EG J1744-3022 SNR G359.1-0.5 SNR G359.1-0.5 PSR B1742-30 PSR B1742-30

Unidentified Sources Type 2: “Dark” Sources Type 2: “Dark” Sources Gamma-ray sources without obvious, extended Gamma-ray sources without obvious, extended counterparts at other wavelengths. Typically counterparts at other wavelengths. Typically extended galactic sources. extended galactic sources. First example First example discovered by HEGRA: discovered by HEGRA: TeV J2032+4130 TeV J2032+4130 Many more discovered by Many more discovered by H.E.S.S. H.E.S.S. Could be a new kind of Could be a new kind of source, a “dark” source, a “dark” accelerator? accelerator?

Unidentified Sources TeV J2032+4130 Update: TeV J2032+4130 Update: Deep observations have revealed faint but extended Deep observations have revealed faint but extended radio and X-ray sources which may be associated to the radio and X-ray sources which may be associated to the very high energy emission making this a very high energy emission making this a “Not-so-dark” source, also the discovery by Fermi of a Not-so-dark” source, also the discovery by Fermi of a “ gamma-ray only pulsar may indicate a PWN scenario. gamma-ray only pulsar may indicate a PWN scenario. 1.4 GHz Radio WSRT Map 1.4 GHz Radio WSRT Map Whipple Whipple HEGRA HEGRA

Could they be PWN? Many of the unidentified H.E.S.S. Sources have a Many of the unidentified H.E.S.S. Sources have a powerful pulsar located near the edge of the powerful pulsar located near the edge of the emission region. With deep enough observations, emission region. With deep enough observations, it's likely that many of these will be added to the it's likely that many of these will be added to the category of “not-so-dark” pulsar wind nebulae. category of “not-so-dark” pulsar wind nebulae.

Offset Pulsar Wind Nebulae Virtually very extended PWN detected by H.E.S.S. is an Virtually very extended PWN detected by H.E.S.S. is an “offset PWN”, i.e. the pulsar lies at the edge of the “offset PWN”, i.e. the pulsar lies at the edge of the emission region. emission region. Two possibilities: Two possibilities: “Crushed” PWN: inhomogeneity in the interstellar Crushed” PWN: inhomogeneity in the interstellar “ medium density prefers expansion in one direction. medium density prefers expansion in one direction. Supersonic Pulsar: pulsar space velocity is greater Supersonic Pulsar: pulsar space velocity is greater than electron diffusion rate. than electron diffusion rate.

Pulsar Correlation Study Correlate HESS Correlate HESS sources with PSRs sources with PSRs from Parkes from Parkes Survey Survey At high Edot/d^2 very At high Edot/d^2 very low probability of low probability of chance coincidence chance coincidence can start to predict can start to predict which PSRs will make which PSRs will make gamma PWNe gamma PWNe

Inverse Compton Gamma-Rays High Energy Electrons scatter CMB photons High Energy Electrons scatter CMB photons through the inverse Compton effect to through the inverse Compton effect to produce Gamma-rays produce Gamma-rays The same electrons produce X-rays and The same electrons produce X-rays and Radio via synchrotron scatter in a local Radio via synchrotron scatter in a local magnetic field magnetic field

Unidentified Gamma-ray Sources as PWNe O.C. De Jager et. al. (2009) Found O.C. De Jager et. al. (2009) Found that as a PWN expands, the average that as a PWN expands, the average magnetic field drops as t^-1.3. Then, magnetic field drops as t^-1.3. Then, the radio/x-ray synchrotron peak will the radio/x-ray synchrotron peak will drop but inverse Compton gamma-rays drop but inverse Compton gamma-rays remain nearly constant for many remain nearly constant for many kiloyears. kiloyears.

Gamma/X Ratio F.Mattana, et. al. Compared ratios of the Gamma- F.Mattana, et. al. Compared ratios of the Gamma- ray/X-ray ratio for PWN associations as a ray/X-ray ratio for PWN associations as a function of time and found a strong correlation, function of time and found a strong correlation, mainly due to falling X-ray components mainly due to falling X-ray components Known PWN Known PWN associations: associations: closed circles closed circles Proposed Proposed associations: associations: open circles open circles

Unidentified HESS J1303-631 Serendipitously discovered by H.E.S.S. In 2004 during Serendipitously discovered by H.E.S.S. In 2004 during observations of the binary system observations of the binary system PSR B1259-63 PSR B1259-63 No extended radio sources found in emission No extended radio sources found in emission region and follow-up observations in X-rays region and follow-up observations in X-rays by Chandra yielded no plausible counterpart by Chandra yielded no plausible counterpart Most likely counterpart: PSR J1301-6305 Most likely counterpart: PSR J1301-6305

Unidentified HESS J1303-631 PSR J1301-6305: PSR J1301-6305: High spin-down power: 1.7e36 erg/sec High spin-down power: 1.7e36 erg/sec Young pulsar: 11,000 years Young pulsar: 11,000 years Distance = 6.6 kpc Distance = 6.6 kpc Gamma-rays represent only a few percent of Gamma-rays represent only a few percent of current spin-down power: typical for PWNe current spin-down power: typical for PWNe

Unidentified HESS J1303-631 Morphology detected at 7 sigma significance Morphology detected at 7 sigma significance Between E<10 TeV and E>10 TeV Between E<10 TeV and E>10 TeV Intrinsic Intrinsic gaussian width gaussian width falls from 0.2 falls from 0.2 to 0.1 deg to 0.1 deg Center of Center of emission moves emission moves ~0.1 degrees ~0.1 degrees Still Still significantly significantly extended above extended above 10 TeV 10 TeV

HESS J1303-631: Gamma-rays The highest energies near the pulsar, lower The highest energies near the pulsar, lower energies farther from pulsar suggests a energies farther from pulsar suggests a pulsar association. pulsar association.